The present invention relates generally to the field of telecommunication system provisioning, and more particularly to a method of and system for provisioning resources in a system where there is overflow from one type of resource into another.
Most North American wireless telecommunication systems are built upon an infrastructure that includes both analog technology, such as Advanced Mobile Phone Service (AMPS), and digital technology, such as Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA). In AMPS technology, each call is carried on a single frequency. In TDMA or CDMA technology, multiple calls are time division multiplexed (TDMA) or code division multiplexed (TDMA) on a single frequency. The multiplexing of several calls on the same frequency provides greater capacity requiring less bandwidth. Partially as a result of the greater capacity provided by newer technologies, wireless operators have been migrating their systems from less efficient technologies to more efficient technologies. In order to balance cost versus quality, wireless operators attempt to provision the minimum number of resources or frequencies necessary to meet specific Grade of Service (GOS) objectives.
Provisioning is typically done according to a mathematical modeling technique. Currently used models include the Poisson Traffic Model and the Erlang B Traffic Model. The Poisson Traffic Model uses the Poisson equation to determine the probability P(i) of a specific number i of simultaneous calls. According to the Poisson Traffic Model       P    ⁢          (      i      )        =            e              -        A              ⁢                  A        i                    i        !            
Where A is the number of Erlangs and
i is the number of simultaneous calls.
Since blocking occurs when all channels are occupied, the Grade of Service, also termed blocking rate, is given by the probability that there are N or more simultaneous calls, where N is the number of channels. Also, since the sum of the probabilities of all possible discrete events must be one, the probability of N or more simultaneous calls P(xe2x89xa7N) is equal to the complementary probability that there are less than N simultaneous calls P( less than N), i.e., P(xe2x89xa7N)=1xe2x88x92P( less than N)
The Poisson Traffic Model determines the grade of service (GOS) by subtracting the sum of the probabilities of events 0 to Nxe2x88x921 from 1 to determine the probability of N or more simultaneous calls. Thus,       P    ⁢          (              ≥        N            )        =      1    -                  e                  -          A                    ⁢                        ∑                      i            =            0                                N            -            1                          ⁢                  xe2x80x83                ⁢                              A            i                                i            !                              
Where A is the number of Erlangs,
i is the number of simultaneous calls, and
N is the number of voice channels.
Currently, wireless system operators provision analog and digital technologies as separate singlemode entities, i.e. they provision analog resources based solely upon analog-only demand, and they provision digital resources based solely upon digital demand. However, most digital capable wireless units are dualmode and capable of operating in either digital mode or analog mode. Thus, if there are insufficient digital channels, a dualmode phone overflows to the analog system. Because of this overflow, wireless operators are finding that the radios they have been provisioning may be inadequate to meet singlemode grade of service objectives. Additionally, the number of digital radios may be excessive to meet their digital grade service objectives. Inadequate analog provisioning leads to subscriber dissatisfaction. Excessive digital provisioning leads to unnecessary cost.
The present invention provides a method of and system for provisioning analog voice channels and digital voice channels in a dual-technology wireless system that includes both singlemode (for example analog-only) and dualmode (analog and digital capable) wireless units. The method determines the number of analog voice channels necessary to produce a desired singlemode grade of service, taking into account overflow of dualmode calls to analog channels, and the number of digital voice channels necessary to produce a desired dualmode grade of service, taking into account the overflow of the dualmode calls to the analog channels. The method may be used to provision channels or to form provisioning tables to enable the determination of the number of analog voice channels and digital voice channels necessary to produce a desired singlemode grade of service for various levels of singlemode and dualmode traffic demand. Preferably, the method of the present invention is based upon an improved Poisson traffic model in which the desired singlemode grade of service is defined by SinglemodeGOS, which is defined by the equation:   SinglemodeGOS  =            (              1        -                              e                          -                              E                a                                              ⁢                                    ∑                              i                =                0                                            A                -                1                                      ⁢                          xe2x80x83                        ⁢                                          E                a                i                                            i                !                                                        )        +                  ∑                  j          =          0                          A          -          1                    ⁢                        (                      1            -                                          e                                  -                                      E                    d                                                              ⁢                                                ∑                                      h                    =                    0                                                        T                    +                    A                    -                    j                    -                    1                                                  ⁢                                  xe2x80x83                                ⁢                                                      E                    d                    h                                                        h                    !                                                                                )                ⁢                  (                                    e                              -                                  E                  a                                                      ⁢                                          E                a                j                                            j                !                                              )                    
where Ea is the number of Singlemode Erlangs,
Ed is the number of Dualmode Erlangs,
T is the number of digital voice channels, and
A is the number of analog voice channels.
Similarly, dualmode Grade of Service is defined by DualmodeGOS, which is determined by the equation:   DualmodeGOS  =            (              1        -                              e                          -                              E                d                                              ⁢                                    ∑                              i                =                0                                            T                -                1                                      ⁢                          xe2x80x83                        ⁢                                          E                d                i                                            i                !                                                        )        +                  ∑                  j          =          0                          A          -          1                    ⁢                        (                      1            -                                          e                                  -                                      E                    a                                                              ⁢                                                ∑                                      h                    =                    0                                    j                                ⁢                                  xe2x80x83                                ⁢                                                      E                    a                    h                                                        h                    !                                                                                )                ⁢                  (                                    e                              -                                  E                  d                                                      ⁢                                          E                a                                  (                                      T                    +                    A                    -                    j                    -                    1                                    )                                                                              (                                      T                    +                    A                    -                    j                    -                    1                                    )                                !                                              )                    
where Ea is the number of Singlemode Erlangs,
Ed is the number of Dualmode Erlangs,
T is the number of digital voice channels, and
A is the number of analog voice channels.
The present invention provides an iterative method of provisioning an optimal number of analog voice channels and digital voice channels in a dual-technology wireless system. It calculates singlemode grade of service as a function of a selected number A of analog voice channels and a selected number T of digital voice channels. If the calculated singlemode grade of service is greater than a specified singlemode grade of service criteria, the method calculates the singlemode grade of service as a function of A+x and T, and as a function of A and T+y, where x is 1 and y is 3 for AMPS/TDMA3 systems. The method then lets A equal A+x if the singlemode grade of service as a function of A+x and T is less than the singlemode grade of service as a function of A and T+y. The method lets T equal T+y if the singlemode grade of service as a function of A and T +y is less than the singlemode grade of service as a function of A+x and T. Then, the method again calculates the singlemode grade of service as a function of A and T.
The method continues until the singlemode grade of service is less than the specified singlemode grade of service criteria, whereupon the method calculates the dualmode grade of service as function of A and T. If the dualmode Grade of Service is more than the specified dualmode GOS criteria, it lets T equal T+y. It then calculates the singlemode GOS as a function of Axe2x88x92x and T. If the singlemode GOS as a function of Axe2x88x92x and T is less than the singlemode GOS criteria it lets A equal Axe2x88x92x. The method repeats until the dualmode grade of service as a function of A and T is less than the specified dualmode grade of service criteria.
Next, the method calculates the average grade of service as a function of A and T, and as a function of A+x and Txe2x88x92y. The average grade of service is calculated according to the equation:                               (          DualmodeTraffic          )                ⁢                  (          DualmodeGOS          )                    +              
            ⁢              xe2x80x83            ⁢                        (          SingleTraffic          )                ⁢                  (          SinglemodeGOS          )                            (              DualmodeTraffic        +        SinglemodeTraffic            )        .
If the average grade of service as a function of A+x and Txe2x88x92y is less than the average grade of service as a function of A and T, and the singlemode and dualmode grades of service as a function of A+x and Txe2x88x92y is less than both the singlemode and dualmode specified grade of service criteria, the method sets A=A+xand T=Txe2x88x92y. Finally, the method calculates the average grade of service as a function of A and T, and as a function of Axe2x88x92x and T+y. If the average grade of service as a function of Axe2x88x92x and T+y is less than the average grade of service as a function of A and T, and the singlemode and dualmode grades of service as a function of Axe2x88x92x and T+y is less than both the singlemode and dualmode specified grade of service criteria, the method sets A=Axe2x88x92x and T=T+y. The method provisions T digital voice channels and A analog voice channels.